It may sound like something straight out of a cartoon, but on the morning of Aug. 30, it was the only thing astronaut Alexander Gerst could think of.

After receiving word from NASA that the International Space Station was very slowly leaking air, Gerst and five other astronauts starting scouring all over for the source. Upon finding the 2-millimeter (0.08-inch) hole in the docked Soyuz MS-09 spacecraft, Gerst did what many of us would likely do — he stuck his finger over the opening.

"Right now Alex has got his finger on that hole and I don't think that's the best remedy for it," NASA's mission control reported over a live feed with the ISS.

To slow the leak, the crew used Kapton, a kind of industrial strength "space tape" that remains stable across extreme temperatures. According to NASA, they later used "epoxy on a gauze wipe to plug the hole completely."

The Soyuz MS-09 crew spacecraft docked to the International Space Station was found to be the source of the small leak in air pressure. The Soyuz MS-09 crew spacecraft docked to the International Space Station was found to be the source of the small leak in air pressure. (Photo: NASA Johnson/Flickr)

The initial theory was either space junk or a small meteorite collided with the station, causing the hole. After closer inspection though, the crew believes the minuscule hole was caused by human error on Earth before the spacecraft even launched into space.

"One of the possibilities is the spacecraft might have been damaged in the final assembly hangar. Or it could happen at the control and testing station, which carried out the final workmanship tests before the spacecraft was sent to Baikonur," a source told Russian news agency TASS.

But was it an innocent mistake by an assemblyman or a more diabolical plot to sabotage the mission?

Dmitry Rogozin, head of the Roscosmos corporation, told TASS that the hole was created by a drill used on the inside of the Soyuz MS-09. "Only those with proper security clearance are allowed to enter. Also, at the entrance to the hangar and the control and measurement station there are security guards checking all those who come and go," another source added.

Either way, an internal investigation is underway.

The good news is, the lives of the astronauts were never in danger, with NASA adding that the "crew are healthy and safe with weeks of air left in the International Space Station reserves."

NASA reports that, as of late Aug. 31, cabin pressure on the ISS is holding steady.

Editor's note: This article has been updated since it was originally published in September 2018.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Astronaut uses finger to plug hole on space station
After finding the source of an air leak on the ISS, astronaut Alexander Gerst did the only thing he could think of.